Referring to FIG. 1, Taiwanese Patent Publication No. 169775 discloses a conventional liquid-cooled motor device including a motor casing 1, a motor 2, an impeller 3 and a coolant casing 4.
The motor casing 1 defines a retaining space 11, and a cooling space 12 surrounding the retaining space 11. The motor 2 is disposed in the retaining space 11, and includes a rotatable output shaft 21. The impeller 3 is co-rotatably mounted to the output shaft 21 of the motor 2. The coolant casing 4 is connected to an end of the motor casing 1, and defines a coolant space 41 that is in fluid communication with the cooling space 12 and that receives the impeller 3 therein, a coolant inlet 42 that is in fluid communication with the coolant space 41, and a coolant outlet 43 that is in fluid communication with the coolant space 41.
When the conventional liquid-cooled motor device is in use (i.e., the motor 2 is in operation), a coolant 5 flows into the coolant space 41 and the cooling space 12 via the coolant inlet 42 for removing heat generated by the motor 2, and exits the coolant space 41 and the coding space 12 via the coolant cutlet 43. The impeller 3 is rotated by the output shaft 21 of the motor 2 to force the flow of the coolant 5.
However, since both of the coolant inlet 42 and the coolant outlet 43 are formed in the coolant casing 4, the coolant 5 flowing into the coolant space 41 via the coolant inlet 42 would hardly flow to an end of the cooling space 12 distal from the coolant casing 4 before the coolant 5 flows out of the coolant space 41 via the coolant outlet 43. Thus, the motor 2 may not be efficiently cooled down. Moreover, the impeller 3 may force the coolant 5 flowing into the coolant space 41 via the coolant inlet 42 to flow out of the coolant space 41 via the coolant outlet 43 without flowing through the cooling space 12.